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Direct Dark Matter Searches

Hans Kraus

• Detector Technologies / Historic

• Cryogenic

• Noble Liquids

A rather selective summary of dark

matter search experiments

Direct Detection Techniques Ar, Xe

ArDM, WARP, XENON, LUX, ZEPLIN

NaI, Ar, Xe

DAMA/LIBRA

ANAIS

NAIAD

KIMS

XMASS

DEAP/CLEAN

Ge

HDMS

GERDA

MAJORANA

IGEX

Si, Ge

CDMS

EDELWEISS

Al2O3 and others CRESST I

CUOPP

PICASSO

CaWO4, ZnWO4 CRESST II

ROSEBUD

Ar, Xe

ArDM, DarkSide, XENON, ZEPLIN-II/III, LUX, Panda-X, LUX-ZEPLIN

NaI, Ar, Xe

DAMA/LIBRA

ANAIS

NAIAD

KIMS

XMASS

DEAP/CLEAN

ZEPLIN-I

Ge

CoGENT

GERDA

MAJORANA

IGEX

Si, Ge

CDMS

EDELWEISS

EURECA

Al2O3 and others CRESST I

CUOPP

SIMPLE

PICASSO

CaWO4, ZnWO4 CRESST II

ROSEBUD

EURECA

Displacement / tracking: DRIFT, Newage, MIMAC, DM-TPC

The Physics Result Landscape

Cryogenic detectors

Initial recoil energy

Displace- ments,

Vibrations

Athermal phonons

Ionization (~30 %)

Thermal phonons (Heat)

Phonon-ionization / phonon-scintillation

Phonon: most precise

total energy measurement

Ionization / Scintillation:

yield depends on recoiling

particle

Nuclear / electron recoil

discrimination.

CRESST Detectors

~6keV signal

Re

sis

tan

ce

[m

]

normal- conducting

super- conducting

T

R

Width of transition: ~1mK

Signals: few K

Stablity: ~ K

tungsten TES Silicon absorber

CaWO4 absorber

300g

tungsten TES

reflecting cavity

CRESST in Gran Sasso

CRESST

CRESST Status (Run 33)

• 18 detector modules mounted (12 standard design, 6 with

active veto for 206Pb recoils)

• Non-blind data set (Aug ’13 to 7th Jan ’14), 377 kg.day to

evaluate performance and define / adjust cuts.

• Data since 7th Jan ’14 to be used in blind analysis.

• Smooth running conditions (>90% duty cycle), 5% removed

due to instabilities (from heavy works in the tunnel).

CRESST Status (crystals and latest result)

Average rate:

~3.5 counts / [kg keV day]

Gamma lines from cosmogenic

activation

Excellent resolution: σ ≈ 100eV

SuperCDMS

CRESST-comm. (2009)

EDELWEISS low thr.

XENON100

LUX

CRESST-TUM40 (2014)

29 kg.days CDMSlite

Expérience pour DEtecter

Les Wimps En SIte

Souterrain

• Search for WIMP dark matter (scattering: ~10keV nuclear recoil with

EDELWEISS-III Detectors From ID detectors to FID detectors

Towards a few × 10−9 pb: EDELWEISS III

Programme under way, funded.

Detector improvements:

• ~40 FID800 detectors to be installed:

24kg fiducial

• 2 NTD heat sensors (better heat ch),

4 ionization channels, instead of 6.

Infrastructure improvements:

• Within the Edelweiss-II setup –

upgrades of cryogenics, cabling,

DAQ, shielding.

• Extra internal PE shield.

EDELWEISS Infrastructure

EURECA

• Further investment into Germanium (EDELWEISS)

and CaWO4 (CRESST) detectors.

• Together with Super-CDMS: target especially low-mass

WIMP window.

• CRESST: background removal, increased scintillation yield.

• EDELWEISS: HEMT readout – lower threshold.

The low-mass WIMP scenario

Low-mass WIMPs:

focus of cryogenic experiments

(EURECA – SuperCDMS).

[but also sensitivity for medium –

high mass WIMPs]

Simple But Important Statements:

“The Sensitivity of a Dark Matter Experiment

Scales as its Mass”

“The problems scale as its Surface Area”

The Noble Liquid Xenon

18

Searches for RARE and LOW

ENERGY events: a challenging

combination

single scatters

S1: prompt scintillation signal

• Light yield: ~60 ph/keV (ER, 0 field)

• Scintillation light: 178 nm (VUV)

• Nuclear recoil threshold ~5 keV

S2: delayed ionisation signal

• Electroluminescence in vapour phase

• Sensitive to single ionisation electrons

• Nuclear recoil threshold ~1 keV

S1+S2 event by event

• ER/NR discrimination (>99.5% rejection)

• mm vertex resolution + high density: self-shielding of radioactive backgrounds

LXe is the leading WIMP target:

• Scalar WIMP-nucleon scattering rate dR/dE ~A2, broad mass coverage (> 5 GeV)

• Odd-neutron isotopes (129Xe, 131Xe) enable SD sensitivity; target exchange possible

• No damaging intrinsic nasties (127Xe short-lived, 85Kr removable, 136Xe 2nbb ok)

Two-phase Xenon TPC Principle

LUX - LUX-ZEPLIN (LZ)

Currently running LUX

LUX-ZEPLIN to use LUX infrastructure

Two-phase Xenon detector

LUX as it was built

The LUX Result (and sensitivity progress)

LUX (2013)-85 live days

LUX +/-1σ expected sensitivity

XENON100(2012)-225 live days

XENON100(2011)-100 live days

ZEPLIN III CDMS II Ge

Edelweiss II

???

• UK-led ZEPLIN programme at Boulby (2001-2011)

– Pioneered two-phase xenon technology

– World class results from 3 xenon experiments

– Fiducial mass ~6 kg

• LUX operating at Sanford Underground Laboratory

– Imperial, Edinburgh and UCL joined after ZEPLIN-III

– Present world-leading experiment

– Fiducial mass ~100 kg

• LZ: next-generation experiment

– LZ formed with MOU between LUX and ZEPLIN-III in 2008

– Selected by DMUK for construction proposal to STFC

– Fiducial mass ~5,600kg (~10-48 cm2 sensitivity)

– Conceptual design nearly completed, construction f. 2015

ZEPLIN LUX LUX-ZEPLIN

The LZ TPC

• TPC PARAMETERS – 1.5 m diameter/length (3x LUX)

– 7 tonne active LXe mass (28x LUX)

– 2x 241 3-inch PMTs (4x LUX)

– Highly reflective PTFE field cage

– 100 kV cathode HV (10x LUX)

– Electron lifetime 3 ms (3x LUX)

PHYSICS PARAMETERS • 5.8 keVr S1 threshold (4.5 keVr LUX)

• 0.7 kV/cm drift field, 99.5% ER/NR disc.

(already surpassed in LUX at 0.2 kV/cm)

TPC CALIBRATION • ER: Dispersed sources: Kr-83m, CH3T

• NR: AmBe, YBe, D-D generator 27

Argon: DEAP-3600 Concept

Staged detector development programme:

MiniCLEAN: measure PSD, prototype

LAr/LNe target exchange to test A2 scaling

DEAP3600: dark matter discovery reach of

10-46 cm2 in 3 tonne-yrs exposure, at

conservative 60 keVr threshold

UK: Calibration, Refrigeration, Veto systems

Open volume of cryogen, surrounded by PMTs in

4π, no electric field, to maximize detected PE per keV

Background strategy: pulse shape discrimination using

fast/slow scintillation to ID recoils and reject 39Ar, self-

shielding of LAr target to mitigate alphas, gammas,

neutrons, + SNOLab depth, active muon veto

DEAP/CLEAN Single Phase Detectors

RHUL Jocelyn Monroe

DEAP-3600 Pulse Shape Discrimination

Summary

Noble liquid detectors (Xe) clearly geared for

exploring very low WIMP-nucleon cross sections.

Cryogenic detectors focus on low-mass WIMPs.